This change attempts to resolve issue #7636: Extract into Function does not
create a generic function with constraints when extracting generic code.
In `FunctionBody::analyze_container`, we now traverse the `ancestors` in search
of `AnyHasGenericParams`, and attach any `GenericParamList`s and `WhereClause`s
we find to the `ContainerInfo`.
Later, in `format_function`, we collect all the `GenericParam`s and
`WherePred`s from the container, and filter them to keep only types matching
`TypeParam`s used within the newly extracted function body or param list. We
can then include the new `GenericParamList` and `WhereClause` in the new
function definition.
This change only impacts `TypeParam`s. `LifetimeParam`s and `ConstParam`s are
out of scope for this change.
075ab03851